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carl_townshend
Frequent Contributor

vlans

I have got 2 vlans on a switch, vlan 1 default, with a 10.0.0.0 ip address, I have added another vlan to the switch, but wanted to give it a 10.1.1.0 class c address, when I try this is comes up with "overlaps with vlan1"

any ideas ?

6 REPLIES 6
amit-singh
Collaborator

Carl,

This is because the mask on Vlan 1 is /8 for the IP 10.0.0.0. When you are defining 10.1.1.0 /24 on another vlan, it is already includes in the addess range 10.0.0.0/8.

Try to give it a different series Ip addrress or change the mack on the vlan 1 to /24.

regards,

-amit singh

if I have a 2 switches, 1 in vlan 1, the other vlan 200, If I have a router plugged into both switches and an ip for each vlan configured on the router, will they see each other ?

Yes, you are mistaking multi vlan trunking through a single interface I think. VLAN's end at the router, any router(unless you are tunneling or using another measure). To the router it will simply look like a network, it doesn't care that it is an artificial segmentation.

Yes, They will. Make sure your router has 2 ethernet ports, Assign the switch vlan an IP and the interface on the router, do the same on other side as well. Ip routing is bydefault enabled on the router and you will be able to route.

regards,

-amit singh

thanks for your help amit, Can you help with this scenario,

I have a network on a flat 10 address. all pc's etc are in vlan 1. We are implementing voIP so we created a seperate vlan, vlan 200, put trunks on etc, each switch can see vlan 200 now. The phones are going on a 10.81.123.x ip address class c, these will be plugged in vlan200. The problem is the phones must get an ip via the dhcp server that gives out these addresses.

the issue is that the dhcp server is giving out addresses to pc's on the network which arent even in vlan 200. I dont know why this is happening, the only way I can think is that because the default router has an ip address on it for both networks ?

can you help

Thanks

Carl

VLANS are broadcast/L3 domains and cannot see each other until they are *told* to - you need to configure inter-VLAN routing.

You have already asked this.

Please take some time and actually read through the responses to your previous posts (http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1dd92e83/15, http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&type=Subscriptions&loc=.1dd92e83/17&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing). Starting or running several different threads makes it difficult to figure out what your problem is, or how others could help.

Relax and follow William's advice :-),

Josef.